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  Flexible cementitious membrane composite and associated crack-isolation floor systemsUSPTO Application #: 20080060299Title: Flexible cementitious membrane composite and associated crack-isolation floor systems Abstract: A method of making the floor crack isolation system includes obtaining a coated, three-ply, flexible membrane and applying it to a subfloor with a deformable adhesive. In a preferred embodiment, a floor crack isolation system includes a membrane and a deformable adhesive. The membrane includes a basemat, having at least three plies, a ply of a meltblown polymer sandwiched between two plies of spunbond polymer; and a flexible coating applied to the basemat, the coating having a cementitious hydraulic component, a polymer comprising a water-soluble, film-forming polymer; and water. The finished membrane is flexible and is bonded to a subfloor with a deformable adhesive. (end of abstract) Agent: Greer, Burns & Crain, Ltd. - Chicago, IL, US Inventors: Ashish Dubey, Peter B. Groza USPTO Applicaton #: 20080060299 - Class: 524031 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080060299. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001]This invention relates to underlayment systems that reduce crack propagation from a subfloor to a finished floor. In one embodiment, a membrane that includes a thin hydraulic layer on a basemat is used with a deformable adhesive as an underlayment for laying ceramic tile. Other embodiments are directed to a floor system with reduced cracking and a method of making it. BACKGROUND OF THE INVENTION [0002]Ceramic tiles and natural stones are both beautiful and practical as surface coverings on floors and walls. They may be waterproof, easily cleaned, durable and can be decorated with an infinite variety of colors and designs. Recently they have become quite popular for use in bathrooms, kitchens and foyers where water is frequently present. [0003]House construction commonly calls for wood to be used as subfloors and drywall to be installed on walls. If wood or drywall is repeatedly exposed to water, it swells as it soaks up water, then contracts as the water evaporates. Repeated cycles of expansion and contraction breaks down the cell walls, causing the substrate to soften, decay and disintegrate over time. When wet, these substrates may also be susceptible to attack by molds, causing additional damage. [0004]If finish surface materials such as ceramic tiles and natural stones are applied directly to wood or drywall, cycles of swelling and drying, and the resultant damage, cause problems with cracking and breaking of the finish surface. Ceramic tiles and natural stones are very rigid and brittle materials, and do not give or stretch when the substrate deflects or moves. When the substrate deflects or moves, the attached tile moves with it causing the tile to crack or break when adjacent areas of substrate move at different rates. If a cracked or broken tile is not replaced immediately, water will be able to seep through the crack, causing even more swelling and drying of the substrate, often resulting further damage to the ceramic tiles. [0005]Typically, 5/16 inch or 1/2 inch (6 mm or 13 mm) cement board, such as DUROCK.RTM. brand cement board manufactured by United States Gypsum Company, Chicago, Ill., is used as a sub-floor underlayment under ceramic tile to provide a compatible surface for bonding to the adhesive tile and to provide an underlayment that does not move laterally. If exposed to water, cement does not swell or degrade and it adds strength and stability under the tiles. [0006]However, the use of cement board has certain disadvantages. A half inch thick cement board weighs about 3 pounds per square foot (13.1 kg/m.sup.2), and can cause fatigue in those who move it to or around the job site or while placing it in position to receive the ceramic tile. Fastening of the cement board to the subfloor requires a large number of fasteners and adds extra labor to the cost of the job. Frequently, the board is cut to fit the underlayment at the edges or to go around corners or cabinets. During and after cutting, alkaline fibers in the dust and exposed edges can be irritating to skin or lungs. Cement board is not waterproof and allows transmission of liquids through it. Thus, attempts have been made in the prior art to find an underlayment that has a good adhesive surface, does not move, yet is lighter in weight and less irritating than cement board. [0007]Plastic sheeting has been used as an underlayment for ceramic tiles. It is thin, lightweight and provides a waterproof barrier. However, plastic has a poor surface for bonding to the mortar used to adhere the tiles. [0008]Thin layers of a lightweight, waterproof concrete composition were used to make concrete canoes by engineering students at several universities for a contest in 2003. The University of Alabama at Huntsville team used a mixture of Portland cement, a latex, an acrylic fortifier, plastic microspheres and water. This mixture produced a composition that had good workability and water resistance. It had a weight of only 14.7 pounds per cubic foot (199 kg/m.sup.3). [0009]U.S. Pat. No. 6,455,615 to Yu discloses a flexible polymer modified cement that can be used alone or on a substrate. It is disclosed for use in concealed areas of construction engineering, water conservancy projects and municipal works. A hydraulic cement, a polymer dispersion and water are calendared to form sheets, then dried until the composition is firm. The hydraulic material optionally includes from 20% to about 50% other hydraulic materials, including fly ash, silica fume, metakaolin and slag. [0010]Even where a flexible sheeting, such as plastic sheeting, is used as an underlayment, it is not effective for reducing damage to the surface finish where the structural subfloor or the subfloor underlayment (hereinafter, collectively the "subfloor") becomes cracked or broken. Typically, traditional floor systems use rigid construction with respect to the bond between the floor finish surfacing material and the substrate. In such systems, the tiles are bonded directly to the substrate using a thin set mortar. If cracks develop in the subfloor, the developed cracks eventually propagate upward through the thin set mortar and the finishing floor surface. [0011]Movement or breaks in the subfloor cause delamination of the underlayment because the underlayment is pulled away from the subfloor at or near the site of the break. Thus, there is a need in the art for a floor underlayment system that allows the membrane to remain attached to the subfloor, even when the subfloor becomes cracked or damaged. Further, there is a need for a floor underlayment system that reduces propagation of cracks in the structural sub-floor or sub-floor overlay from propagating to the floor finish surface. SUMMARY OF THE INVENTION [0012]These and other needs are addressed by an improved underlayment system that includes a membrane for use as an underlayment for ceramic tile and an adhesive for attaching the membrane to the structural subfloor or the subfloor overlay. The membrane is flexible and includes a basemat to which a flexible coating is applied. The adhesive is deformable. [0013]In a preferred embodiment, an underlayment system includes a flexible membrane having a basemat that includes at least three plies, a center ply of a meltblown polymer sandwiched between two plies of spunbond polymer; and a flexible coating applied to the basemat, the coating having a hydraulic component, a polymer comprising a water-soluble, film-forming polymer; and water. Use of this specific basemat to make a coated membrane results in a product that is waterproof, soft to the touch, strong and extremely flexible even though coated with a hydraulic cementitious slurry. The spunbond layers hold the slurry, which binds the fibers in those layers into a crystalline matrix as the hydraulic material hydrates. The membrane is attached to the subfloor using a deformable adhesive. [0014]In another embodiment of the floor underlayment system, the membrane includes a flexible basemat to which is applied a coating. The coating includes a polymer and a hydraulic material comprising at least 50% fly ash. [0015]Yet another embodiment is to a flooring system that includes the subfloor, the flexible membrane, the deformable adhesive and a finish floor component. A method of making a crack isolation system includes obtaining a flexible membrane comprising a basemat and a coating on at least one surface of the basemat, providing a deformable adhesive; and applying the deformable adhesive between a subfloor and the membrane. [0016]The waterproof membrane for use between a substrate and ceramic tiles is obtained that is extremely flexible and resilient. It has very good tolerance to damage, even after severe, repeated deformation cycles. The membrane has good moisture resistance and moisture durability. The slurry sets very rapidly, especially when dried in an oven or kiln. There is virtually no plastic shrinkage induced cracking as the product dries. Water demand for processing is very low, and the mixture is flowable and self-leveling even at low water addition rates. [0017]When combined with a deformable adhesive, this membrane is part of a floor crack isolation system that reduces propagation of cracks in the subfloor from percolating upward to cause damage to the finish floor. When cracks occur, both the adhesive and the membrane stretch and deform, absorbing the lateral forces that attempt to move pieces of the finish floor or sections of the grout in the vicinity of the crack. Since less stress passes through to the visible portion of the flooring, it is less likely to crack or break. Such a floor system requires less maintenance than conventional flooring. It will have to be regrouted less frequently. It is less likely to require replacement of broken tiles or other flooring pieces. DETAILED DESCRIPTION OF THE INVENTION [0018]Flexible hydraulic materials are made suitable for use, among other things, as underlayment for ceramic tiles. Unless otherwise noted, amounts or concentrations reported herein describing the compositions are on a weight basis, exclusive of any water that may be present. [0019]In a first embodiment, a flexible membrane is coated with a cementitious coating that includes fly ash. Any hydraulic materials are useful in the coating composition of this invention. Class C hydraulic fly ash, which is a high lime content fly ash obtained from the processing of certain coals, or its equivalent, is the most preferred hydraulic material. ASTM designation C-618 describes the characteristics of Class C fly ash (Bayou Ash Inc., Big Cajun, II, La.). When mixed with water, the fly ash sets similarly to a cement or gypsum. Use of other hydraulic materials in combination with fly ash are contemplated, including cements, including high alumina cements, calcium sulfates, including calcium sulfate anhydrite, calcium sulfate hemihydrate or calcium sulfate dihydrate, lime, other hydraulic materials and combinations thereof. Mixtures of fly ashes are also contemplated for use. Silica fume (SKW Silicium Becancour, St. Laurent, Quebec, Calif.) is another preferred material. [0020]While not wishing to be bound by theory, it is believed that the shape of the fly ash particle contributes to the Theological characteristics of this coating. The substantially spherical shape of fly ash creates a "ball bearing" effect in the mix, improving workability of the coating without increasing water requirements. In addition, some fly ashes have been shown to significantly decrease heat generation as the concrete hardens and strengthens. Fly ash, as do all pozzolanic materials, generally provides increased strength gain for much longer periods than mixes with Portland cement (St. Mary's Cement Inc., Detroit, Mich.) only. Continue reading... Full patent description for Flexible cementitious membrane composite and associated crack-isolation floor systems Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Flexible cementitious membrane composite and associated crack-isolation floor systems patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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